Van Borm S, Jonges M, Lambrecht B, Koch G, Houdart P, van den Berg T
Department of Virology, Veterinary and Agrochemical Research Center, Ukkel, Belgium.
Transbound Emerg Dis. 2014 Feb;61(1):86-90. doi: 10.1111/tbed.12009. Epub 2012 Sep 20.
The 2003 outbreak of Highly pathogenic avian influenza (HPAI) A(H7N7) in the Netherlands, Belgium and Germany resulted in significant genetic diversification that proved informative for tracing transmission events. Building on previous investigations on the Dutch outbreak, we focused on the potential transnational transmissions between the Netherlands and Belgium. Although no clear epidemiological links could be identified from the tracing data, the transmission network based on concatenated HA-NA-PB2 sequences supports at least three independent introductions from the Netherlands to Belgium and suggests one possible introduction form Belgium back to the Netherlands. Two introductions in the Belgian province of Limburg occurred from nearby farms in the Dutch province of Limburg. One introduction resulted in three secondary infected farms, while a second introduction did not cause secondary infections. The third introduction into Belgium occurred in the north of the Antwerp province, very close to the national border, and originated from the North of the Dutch province Brabant (long distance transmission, >65 km). The virus spread to two additional Belgian farms, one of which may be the source of a secondarily infected farm in the Netherlands. One infected turkey farm in the province of Antwerp (Westmalle) was geographically close to the latter introduction, but genetically clustered with the first introduction event in the Limburg province. Epidemiological tracing data could neither confirm nor exclude whether this outbreak was a result from long distance contacts within Belgium or whether this farm presented a fourth independent transboundary introduction. These multiple transnational transmissions of HPAI in spite of reinforced biosecurity measures and trade restrictions illustrate the importance of international cooperation, legislation and standardization of tools to combat transboundary diseases.
2003年荷兰、比利时和德国爆发的高致病性甲型禽流感（HPAI）A（H7N7）导致了显著的基因多样化，这被证明有助于追踪传播事件。基于之前对荷兰疫情的调查，我们重点关注了荷兰和比利时之间的潜在跨国传播。尽管从追踪数据中无法确定明确的流行病学联系，但基于HA-NA-PB2串联序列构建的传播网络支持至少三次从荷兰独立传入比利时的情况，并表明有一次可能是从比利时传回荷兰。比利时林堡省的两次传入分别来自荷兰林堡省附近的农场。一次传入导致三个农场继发感染，而另一次传入未引起继发感染。第三次传入比利时发生在安特卫普省北部，非常靠近国界，源头是荷兰布拉班特省北部（远距离传播，>65公里）。该病毒传播到另外两个比利时农场，其中一个可能是荷兰一个继发感染农场的源头。安特卫普省（韦斯特马勒）的一个感染火鸡农场在地理位置上靠近后一次传入，但在基因上与林堡省的第一次传入事件聚类。流行病学追踪数据既不能证实也不能排除此次疫情是比利时境内远距离接触的结果，或者该农场是否代表了第四次独立的跨境传入。尽管采取了强化生物安全措施和贸易限制，HPAI的这些多次跨国传播说明了国际合作、立法以及应对跨境疾病工具标准化的重要性。
